Embodiments of the present invention relate generally to power supply enclosures, and more particularly to an arc fault path for mitigation of an arc fault in a power supply enclosure.
Power supplies configured to contain, redirect, mitigate and or control a flow of pressure and heat-energy between a first alternating current (AC) system and a second AC system are used in a variety of commercial and industrial applications. For example, a power supply is typically used in AC motor control and operation systems. Various power supplies convert energy from a first frequency and voltage to a second variable frequency; which may include direct current (DC) and or AC power of fixed or variable frequency. One way to implement such a power supply is a drive including one or more power cells, each power cell including multiple solid state converters with an intermediate direct current (DC) link. One exemplary system incorporating such power cells is discussed in U.S. Pat. No. 5,625,545 to Hammond (the '545 patent), the disclosure of which is hereby incorporated by reference in its entirety as if fully set forth herein.
In certain applications, multi-cell power supplies utilize modular power cells to process power between a source and a load. Such modular power cells can be applied to a given power supply with various degrees of redundancy to improve the availability of the power supply. For example, FIG. 1 illustrates various embodiments of a prior art power supply (e.g., an AC motor drive) having nine such power cells. The power cells in FIG. 1 are represented by a block having input terminals A, B, and C; and output terminals T1 and T2. In FIG. 1, a transformer or other multi-winding device 110 receives three-phase, medium-voltage power at its primary winding 112, and delivers power to a load 130 such as a three-phase AC motor via an array of single-phase inverters (also referred to as power cells). Each phase of the power supply output is fed by a group of series-connected power cells, called herein a “phase-group”.
The transformer 110 includes primary windings 112 that excite a number of secondary windings 114-122. Although primary winding 112 is illustrated as having a star configuration, a mesh configuration is also possible. Further, although secondary windings 114-122 are illustrated as having a delta or an extended-delta configuration, other configurations of windings may be used as described in the '545 patent. In the example of FIG. 1 there is a separate secondary winding for each power cell. However, the number of power cells and/or secondary windings illustrated in FIG. 1 is merely exemplary, and other numbers are possible. Additional details about such a power supply are disclosed in the '545 patent.
A number of ranks of power cells are connected between the transformer 110 and the load 130. A “rank” in the context of FIG. 1 is considered to be a three-phase set, or a group of three power cells established across each of the three phases of the power delivery system. Referring to FIG. 1, rank 150 includes power cells 151-153, rank 160 includes power cells 161-163, and rank 170 includes power cells 171-173. A master control system 195 sends command signals to local controls in each power cell over fiber optics or another wired or wireless communications medium 190. It should be noted that the number of power cells per phase depicted in FIG. 1 is exemplary, and more than or less than three ranks is possible in various embodiments.
A power supply such as is described in the '545 patent is housed in an enclosure. Arc faults may occur within such power supply enclosures; discussion of detection of arc faults in a power supply enclosure is found in U.S. Pat. No. 7,579,581 to Aiello et al., filed May 18, 2007, which is herein incorporated by reference in its entirety as if fully set forth herein.